Agent for desulfurizing crude iron and steel melts, and process for making it

Abstract

The invention provides an agent for desulfurizing crude iron and steel melts, the desulfurizing agent being based on calcium carbide containing calcium oxide. The desulfurizing agent is produced by admixing a calcium carbide melt having up to 45 weight % of calcium oxide therein with an excess of 3 to 15 weight %, based on the CaO-content of more than 45 up to 80 weight % desired for the final product, of calcium oxide. The resulting mixture is allowed to solidify and cool down to temperatures of 350° to 450° C. Next, the solidified melt is precrushed to material with a size of less than 150 mm. Particles with a size of less than 4 mm are screened off and the remaining material is comminuted, with the exclusion of moisture, to material with a size of less than 10 mm.

We claim: 
     
       1. An agent for desulfurizing crude iron and steel melts, the desulfurizing agent consisting of calcium carbide and calcium oxide and being produced by the steps comprising: preparing a calcium carbide melt containing up to 45 weight % of calcium oxide; introducing into the melt fine particulate calcium oxide in a total amount of more than 48 up to 95 weight % of the final product; allowing the resulting molten mixture to solidify and cool down to a temperature of 350° to 450° C.; precrushing the solidified melt at that temperature to material with a size of less than 150 mm; screening off particles with a size of less than 4 mm; and further crushing and grinding the remaining material, with the exclusion of moisture, to material with a size of less than 10 mm. 
     
     
       2. A process for making an agent for desulfurizing crude iron and steel melts, the desulfurizing agent consisting of calcium carbide and calcium oxide, which process comprises: making a desulfurizing agent containing 20 to 55 weight % of calcium carbide and more than 45 up to 80 weight % of calcium oxide by introducing into a calcium carbide melt containing up to 45 weight % of calcium oxide fine particulate calcium oxide in a total amount of more than 48 up to 95 weight % of the final product; allowing the resulting molten mixture to solidify and cool down to a temperature of 350° to 450° C.; precrushing the solidified melt at that temperature to material with a size of less than 150 mm; screening off particles with a size of less than 4 mm; and further crushing and grinding the remaining material, with the exclusion of moisture, to material with a size of less than 10 mm. 
     
     
       3. The process as claimed in claim 2, wherein the calcium oxide is introduced into the calcium carbide melt inside a crucible. 
     
     
       4. The process as claimed in claim 2, wherein calcium oxide preheated to temperatures up to 2000° C. is introduced into the calcium carbide melt, the calcium oxide being preheated to a temperature which is the higher up to 2000° C. the higher the proportion of additionally dissolved calcium oxide to be established within the range 45 to 80 weight %. 
     
     
       5. The process as claimed in claim 2, wherein the calcium carbide melt used as feed melt contains 20 to 45 weight % of calcium oxide. 
     
     
       6. The process as claimed in claim 2, wherein the particles with a size of less than 4 mm screened off after the precrushing step are recycled.